C# 判断字符为空的6种方法的效率实测对比

2020-01-24 01:10:32

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C#中提供了相当丰富的方法或属性来判断一个字符是否为空，常用的方法有以下6种

1. strTest== ""

2. strTest.Equals("")

3. strTest== string.Empty

4. strTest.Equals(string.Empty)

5. strTest.Length == 0

6. string.IsNullOrEmpty(strTest)

为了对以上6种方法的效率，有个直观的感受，我特意编写了以下的测试代码：

using System;namespace StrTest{  class Program  {    //定义3个字符串 以便测试在多种情况下 下面6种判断方法的速度    public static string strTest01 = "";    public static string strTest02 = string.Empty;    public static string strTest03 = "0123456789";    public static DateTime start, end; //定义开始时间 和 结束时间    public static TimeSpan ts;    //定义两个时间的间隔    //**********************对strTest使用6种测试方法*****************************    public static void Test(string strTest)    {      //string == ""      start = DateTime.Now;      for (int counter = 0; counter <= 100000000; counter++)      {        if (strTest == "")        {        }      }      end = DateTime.Now;      ts = end - start;      Console.WriteLine("string == /"/" 时间消耗为 " + ts.TotalSeconds + " 秒");      //string.Equals("")      start = DateTime.Now;      for (int counter = 0; counter <= 100000000; counter++)      {        if (strTest.Equals(""))        {        }      }      end = DateTime.Now;      ts = end - start;      Console.WriteLine("string.Equals(/"/") 时间消耗为 " + ts.TotalSeconds + " 秒");      //string == stirng.Empty      start = DateTime.Now;      for (int counter = 0; counter <= 100000000; counter++)      {        if (strTest == string.Empty)        {        }      }      end = DateTime.Now;      ts = end - start;      Console.WriteLine("string == string.Empty 时间消耗为 " + ts.TotalSeconds + " 秒");      //string.Equals(string.Empty)      start = DateTime.Now;      for (int counter = 0; counter <= 100000000; counter++)      {        if (strTest.Equals(string.Empty))        {        }      }      end = DateTime.Now;      ts = end - start;      Console.WriteLine("string.Equals(string.Empty) 时间消耗为 " + ts.TotalSeconds + " 秒");      //string.Length == 0      start = DateTime.Now;      for (int counter = 0; counter <= 100000000; counter++)      {        if (strTest.Length == 0)        {        }      }      end = DateTime.Now;      ts = end - start;      Console.WriteLine("string.Length == 0 时间消耗为 " + ts.TotalSeconds + " 秒");      //string.IsNullOrEmpty(string)      start = DateTime.Now;      for (int counter = 0; counter <= 100000000; counter++)      {        if (string.IsNullOrEmpty(strTest))        {        }      }      end = DateTime.Now;      ts = end - start;      Console.WriteLine("string.IsNullOrEmpty(string) 时间消耗为 " + ts.TotalSeconds + " 秒" + "/n");    }    static void Main(string[] args)    {      Console.WriteLine("=======================================");      Console.WriteLine("strTest = /"/" 的5种测试结果");           Console.WriteLine("=======================================");      Test(strTest01);      Console.WriteLine("=======================================");      Console.WriteLine("strTest = string.Emtpy 的5种测试结果");       Console.WriteLine("=======================================");      Test(strTest02);      Console.WriteLine("=======================================");      Console.WriteLine("strTest = /"0123456789/" 的5种测试结果");       Console.WriteLine("=======================================");      Test(strTest03);      Console.ReadLine();  //等待键盘的输入 作用:使屏幕暂停在此处    }  }}

我把能关的软件都关闭掉了尽可能的屏蔽掉系统影响并且让6种方法都运行了1亿次

第一次的截图：

第一次测试结果